package com.buba.utils;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * @author lj
 * @Type AgeUtil
 * @Desc
 * @date 2022/6/21 9:24
 */
public class AgeUtil {
    /**
     * 根据生日计算年龄
     * @param birthdayStr 生日字符串：yyyy-MM-dd
     * @return
     */
    public static int getAgeByBirth(String birthdayStr) {

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date birthday = sdf.parse(birthdayStr);
            //Calendar：日历
            /*从Calendar对象中或得一个Date对象*/
            Calendar cal = Calendar.getInstance();
            /*把出生日期放入Calendar类型的bir对象中，进行Calendar和Date类型进行转换*/
            Calendar bir = Calendar.getInstance();
            bir.setTime(birthday);
            /*如果生日大于当前日期，则抛出异常：出生日期不能大于当前日期*/
            if(cal.before(birthday)){
                throw new IllegalArgumentException("The birthday is before Now,It's unbelievable");
            }
            /*取出当前年月日*/
            int yearNow = cal.get(Calendar.YEAR);
            int monthNow = cal.get(Calendar.MONTH);
            int dayNow = cal.get(Calendar.DAY_OF_MONTH);
            /*取出出生年月日*/
            int yearBirth = bir.get(Calendar.YEAR);
            int monthBirth = bir.get(Calendar.MONTH);
            int dayBirth = bir.get(Calendar.DAY_OF_MONTH);
            /*大概年龄是当前年减去出生年*/
            int age = yearNow - yearBirth;
            /*如果出当前月小与出生月，或者当前月等于出生月但是当前日小于出生日，那么年龄age就减一岁*/
            if(monthNow < monthBirth || (monthNow == monthBirth && dayNow < dayBirth)){
                age--;
            }
            return age;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return -1;

    }
}
